The present invention relates to an optical pickup device and to a method of manufacturing the same. More particularly, the present invention relates to a technique of supporting an objective lens of an optical pickup device.
An optical pickup device used for reproducing/recording information in an optical recording medium is described in, for example, Japanese Patent Publication No. 4-49174B2. As shown in FIGS. 8 and 9, the optical pickup device described in the publication has an objective lens 11 for converging a laser beam originating from a light source (not depicted) onto an optical recording medium (not depicted), and a lens holder 12 for sustaining the objective lens 11. A drive coil 13 for focus-correction purpose (hereinafter called xe2x80x9cfocus-correction drive coil 13xe2x80x9d) is wound around the lens holder 12. Further, a pair of drive coils 14 for tracking correction purpose (hereinafter called xe2x80x9ctracking-correction drive coils 14xe2x80x9d) are bonded to each of opposed side faces of the lens holder 12.
In the optical pickup device 10, the lens holder 12 is elastically supported in a cantilever fashion by four metal wires 16A, 16B, 16C, and 16D. The four wires 16A, 16B, 16C, and 16D extend from a fixation member 110 and act as members for feeding power to the lens holder 12. The wires 16A to 16D are coated with insulation material 15 such as a rubber tube or resin. In each of the wires 16A to 16D, a base end 161 is fixed to the fixation member 110, and a leading end 162 passes through a hole 12a formed in opposed side faces of the lens holder 12, wherein the holes 12a are formed in upper and lower areas of the side faces. The leading end 162 is soldered to a printed board 17 disposed on either lateral side face of the lens holder 12.
The ends of the drive coil 13 and the ends of the drive coil 14 are soldered to the respective printed boards 17. The focus-correction drive coil 13 and the tracking-correction drive coils 14 are electrically connected to the four wires 16A through 16D by way of copper foil patterns of the printed boards 17.
The base end 161 of each of the wires 16 is soldered to a printed board 18 (i.e., the side of the printed board 18 on which is mounted the fixation member 110). The printed board 18 is fixed to the side of the C-shaped fixation member 110 through use of a screw 19. The fixation member 110 is formed from magnetic material, and two magnets 111 are bonded to the interior side of the fixation member 110, thus constituting a magnetic circuit in conjunction with the focus-correction drive coil 13 and the tracking-correction drive coils 14. Lead wires 112 are soldered to the printed board 18 and are electrically connected to the wires 16A through 16D by way of a copper foil pattern of the printed board 18.
In the optical pickup device 10 having the foregoing construction, when power is fed to the lead wires 112, power is fed to the focus-correction drive coil 13 or to the tracking-correction drive coils 14 by way of the wires 16A through 16D. By magnetic force developing between the focus-correction drive coil 13 or the tracking-correction drive coils 14 and the magnets 111, the lens holder 12 is moved in a focusing or tracking direction so as to oppose the elastic force of the wires 16A to 16D while deforming the wires 16A to 16D. Consequently, the objective lens 11 is also moved in either the focusing or tracking direction. Accordingly, a laser beam originating from a light source (not depicted) is radiated onto a predetermined position on an optical recording medium by way of the objective lens 11. If the light reflected from the recording medium is detected, information can be recorded onto and reproduced from the optical recording medium.
As shown in FIG. 10A, the four wires 16A to 16D are arranged in parallel to each other such that they overlap in sets of two when viewed in either the focusing direction (designated by arrow F) or the tracking direction (designated by arrow T). As shown in FIG. 10B, when viewed from the base ends of the four wires 16A through 16D, the wires 16A through 16D are arranged independently of each other within a rectangular-parallelepiped space (with the shorter sides of the rectangular-parallelepiped space extending in the focusing direction and the longer sides thereof extending in the tracking direction). Further, each of the wires 16A to 16D is formed from a wire having a uniformly-circular cross section.
Demands exists for a more compact and slim optical pickup device 10. However, the optical pickup device 10, in which the lens holder 12 is supported by the wires 16A through 16D as described by reference to FIGS. 10A and 10B, cannot satisfy such a demand in many cases. For instance, realization of a compact and slim optical pickup device 10 involves high-density layout of components. However, the wires 16A through 16D are placed in the corners of the rectangular-parallelepiped space, as shown in FIGS. 10A and 10B, and hence this space becomes dead space.
When the related optical pickup device 10 has been made compact and slim, difficulty is encountered in moving the lens holder 12 appropriately in the focusing direction or in the tracking direction. If the lens holder 12 is made compact and slim in association with the optical pickup device 10 having been made compact and slim, the wires 16A through 16D become closer to each other in both the focusing and tracking directions. Accordingly, the attitude of the lens holder 12 during movement of the lens holder 12 in either the focusing or tracking direction becomes difficult to control. If the wires 16A to 16D become closer to each other in the focusing direction as a result of the lens holder 12 being made slim, the wires 16A through 16D become likely to twist in the focusing direction. Hence, when moved in the tracking direction, the lens holder 12 becomes likely to tilt. If the wires 16A through 16D become closer to each other in the tracking direction as a result of a decrease in the width of the lens holder 12, the wires 16A through 16D become likely to twist in the tracking direction. Accordingly, when moved in the focusing direction, the lens holder 12 becomes likely to tilt.
In the light of drawbacks of the related optical pickup device, the object of the present invention is to provide an optical pickup device which enables a reduction in dead space, even when adopting a construction of supporting a lens holder with four wires in view of effective feed of power.
Further, another object of the present invention is to provide an optical pickup device which enables a reduction in dead space and appropriate movement of a lens holder in both focusing and tracking directions, as well as to provide a method of manufacturing the optical pickup device.
In order to achieve the above objects, according to the present invention, there is provided an optical pickup device for an optical recording medium, comprising:
an objective lens for converging a laser beam onto the optical recording medium;
a lens holder for holding the objective lens;
fixation member;
four wires, first ends of which is supported by the fixation member, and second ends of which is connected to the lens holder; and
a lens driver for moving the objective lens in a focusing direction and a tracking direction of the optical recording medium, by elastically deforming the four wires through use of a magnetic force,
wherein the four wires are arranged so as to form two sets of wires and such that the two wires in each set overlap when viewed from at least one of the focusing direction and the tracking direction; and
wherein the two wires in at least one set of the two sets are integrally fixed together.
In terms of use of four wires for feeding power to a lens holder, there is a commonality between the present invention and the related device. However, the present invention differs from the related device in that, of the two sets of wires arranged so as to overlap when viewed from the focusing or tracking direction, two wires of at least one of the two sets are integrally fixed together.
Preferably, the wires in a first set are integrally fixed together like one wire, while the wires in a second set are separated. In this configuration, the triangular arrangement of the four wires can reduce dead space to a greater extent than can a rectangular arrangement of four wires.
More preferably, the four wires are arranged so as to form an isosceles triangle when viewed from an extending direction of the wires. The wires in the first set are arranged in a position corresponding to an apex of the isosceles triangle, and the wires in the second set are arranged in positions corresponding to remaining vertices of the isosceles triangle. In this configuration, the deformation of the wires under a good balance can be realized.
Preferably, the set formed from the integrally-fixed two wires is arranged on the apex of an isosceles triangle, and the independent two wires of the other set are arranged on the remaining vertices of the isosceles triangle.
Preferably, the wires in each set are integrally fixed together like one wire. In this configuration, since the wires are arranged as if there were two wires, a dead space can be reduced to a greater extent than can rectangular arrangement of four wires.
Preferably, the wires are fixed together by heat sealing an insulative resin material. In this configuration, the wires can be readily insulated and bonded together.
Preferably, at least one wire is provided with a portion squeezed from at least one of the tracking direction and the focusing direction. If the wires are squeezed from the tracking direction, the wires are likely to deflect in the tracking direction but less likely to deflect in the focusing direction. Conversely, if the wires are squeezed from the focusing direction, the wires are likely to deflect in the focusing direction but less likely to deflect in the tracking direction. If the direction in which wires are to be squeezed is determined in accordance with specifications and characteristics of an optical pickup device, to thereby effect modification for imparting orientation to ease of flexure of the wires, there can be prevented occurrence of a failure, such as inclination of the lens holder (or an objective lens), which would otherwise be caused when the lens holder is moved in either the focusing or tracking direction. Since parts of wires are squeezed, the remaining portions of the wires become more easily deformed in the direction orthogonal to the direction in which the wires are squeezed. Ease of flexure of wires can be arbitrarily adjusted by determining the longitudinal extent over which the wires are to be squeezed or the thicknesswise extent to which the wires are to be squeezed. Even when there arises a necessity of adjusting the elasticity of the wires for appropriately moving the lens holder (objective lens) when the optical pickup device is made compact and slim, such a demand can be readily and appropriately satisfied, thus yielding an advantage of achieving a high degree of design freedom of the optical pickup device.
Preferably, the wires in each set are provided with a portion squeezed from at least one of the tracking direction and the focusing direction.
In this configuration, even when the wires are spaced closer to each other in the focusing direction, the wires are less likely to be distorted. Hence, the lens holder does not tilt when moved in the tracking direction. Since appropriate ease of flexure in the focusing direction still remains in the remaining portions of the wires, no problem is encountered in moving the lens holder (objective lens) in the focusing direction.
Conversely, in a case where portions of the respective four wires are squeezed from the focusing direction, the wires become less likely to be deformed in the tracking direction. Hence, if the wires are spaced closer to each other in the tracking direction when the width of the lens holder is made smaller, the wires are less likely to be distorted in the tracking direction. Hence, when moved in the focusing direction, the lens holder does not tilt. Since appropriate ease of flexure in the tracking direction still remains in the remaining portions of the wires, no problem is encountered in moving the lens holder (objective lens) in the tracking direction.
Preferably, the squeezed portion includes a first portion squeezed from the tracking direction and a second portion squeezed from the focusing direction. In this configuration, when the lens holder is moved in the focusing direction, the wires are deflected in the portions squeezed from the tracking direction. However, the thus-squeezed portions are less likely to deflect in the tracking direction, thus preventing inclination of the lens holder (objective lens). When the lens holder is moved in the tracking direction, the wires are deflected in the portions squeezed from the tracking direction. However, the thus-squeezed portions are less likely to deflect in the focusing direction, thus preventing inclination of the lens holder (objective lens). Further, since ease of flexure of the wires can be adjusted by determining the longitudinal range and thicknesswise extent over which the wires are to be squeezed, in accordance with specifications and characteristics of the optical pickup device, the characteristics of the wires can be adjusted and corrected, thereby yielding an advantage of great improvement in the degree of design freedom of an optical pickup device.
According to the present invention, there is also provided a manufacturing method of an optical pickup device for an optical pickup device, comprising the steps of:
providing a lens holder for holding an objective lens for converging a laser beam onto the optical recording medium, a fixation member, and four wires;
connecting the fixation member and the lens holder via the four wires such that the four wires are arranged so as to form two sets of wires, and such that the two wires in each set overlap when viewed from at least one of the focusing direction and the tracking direction; and
squeezing a portion of at least one of the wires from at least one of a focusing direction and a tracking direction of the optical recording medium.
In this configuration, on the basis of actual movement of the lens holder (objective lens), the characteristics of the wires can be adjusted.
Preferably, the two wires arranged so as to overlap when viewed from at least one of the focusing direction and the tracking direction are squeezed simultaneously. Alternatively, the two wires in each set are squeezed simultaneously.
In this configuration, on the basis of actual movement of the lens holder (objective lens), the characteristics of the wires can be efficiently adjusted. Two wires to be squeezed simultaneously can be squeezed to substantially the same extent.